Plasma uniformity control during plasma processing for treating semiconductor substrates is important to achieve patterning structures on a substrate or controlling the amount of material removed from or deposited on or into the substrate. One aspect of process performance may be related to the plasma density across the substrate which may determine the uniformity of the plasma treatment across the substrate. In some instances, the plasma density near or at the edge of the substrate may vary at a higher rate than at the interior area of the substrate. The plasma density may vary due to the influence of the chamber wall or the focus rings that may be adjacent to the substrate. For example, the plasma ions may be attracted to or lost to the peripheral components (e.g., chamber wall, focus ring) caused by the potential difference between the interior and exterior portions inside the plasma chamber. Accordingly, systems and methods that can control or vary the potential difference to minimize the changes in plasma density at the edge of the substrate may be desirable.